Is your min pin on flea prevention? If not, please start that first, even if you are not seeing any fleas. I recommend Advantage or Advantix because you can use it every 2-3 weeks to initially get fleas under control. It is very important to treat your yard and home also. Vaccuum often. I would definitely consider environmental allergies as a definite possibility, especially with the chewing on the paws. The prednisone usually helps a lot with this, but other infections may be comtemplating this. Did your vet do any skin scrapings, skin impressions or ringworm test? What is in the shampoo? The skin scraping would check for skin mites. The skin impression will check for bacterial and/or yeast infections on the skin, which is often the case with self trauma and swelling. She may need to be antibiotics or antifungal medication. While ringworm tends to be a more uncommon disease, it can mimic most skin diseases in dogs. You can also try omega fatty acids to help the skin, but this is more of a secondary treatment. Please let me know if you have anymore questions. Hope this helps.